1. Field of the Invention
The present invention relates to an anti-glare film manufacturing method, and particularly, to an anti-glare film manufacturing method which includes: forming an ultraviolet curable resin including particles on a film substrate; and curing the ultraviolet curable resin by ultraviolet irradiation to form an anti-glare layer.
2. Description of the Related Art
In recent years, there is increasing demand for optical films. Representative examples of the optical film include films having various functions such as an optical compensation film which is used as a retardation film for a liquid crystal cell, an anti-reflective film, and an anti-glare film.
As a representative optical film manufacturing method, there is a method which includes: applying a coating liquid to a surface of a strip-like flexible support (hereinafter, referred to as “web”) by using various coating devices; drying the coating liquid; and curing the coating liquid to form a coating film having various compositions. In many cases, an ultraviolet (UV) curing unit is employed in the curing.
The curing efficiency in the UV curing process is important. Particularly, it is known that when oxygen is present, the oxygen becomes an inhibitory factor in the course of the polymerization and crosslinking, whereby the strength of the coating film and the bonding property between the coating film and the web which is a base substrate are reduced, and furthermore, the hardness, adhesion force and the like of the coating film are reduced.
Generally, the coating film is formed by polymerizing using UV light a low-molecular resin, which is referred to as a monomer, to be a high-molecular resin, but in many cases, the oxygen concentration is lowered under the UV irradiation. The reason for this is that under the UV irradiation, a radical that is generated from the initiator plays a major roll in the resin polymerization, but when oxygen is present, the radical is eliminated. Accordingly, it is important to lower the oxygen concentration.
Hitherto, there are various proposals as methods and devices for coping with the presence of oxygen (see JP1999-104562A (JP-H11-104562A)).
This proposal employs a configuration in which an UV-irradiated portion is filled with an inert gas to remove the oxygen. Specifically, the entire irradiated portion is covered with a metallic member or the like and an inert gas is introduced therein. Therefore, the oxygen concentration in the UV-irradiated portion can be kept to 1000 ppm or lower.
In addition, there is a proposal to obtain a uniform surface hardness only with a small unevenness in curing while reducing the inert gas consumption (see JP1999-268240A (JP-H11-268240A)). This proposal employs a configuration in which an ultraviolet irradiator and a reaction chamber are isolated from each other and a sealing mechanism is provided at a reaction chamber entrance in order to lower the oxygen concentration in the reaction chamber.